1. Field of the Invention
This invention relates to fabric laminates having excellent ballistic resistant properties. More particularly, the invention pertains to a reinforced, delamination resistant, ballistic resistant composites.
2. Description of the Related Art
Ballistic resistant articles containing high strength fibers that have excellent properties against deformable projectiles are known. Articles such as bullet resistant vests, helmets, vehicle panels and structural members of military equipment are typically made from fabrics comprising high strength fibers. High strength fibers conventionally used include polyethylene fibers, para-aramid fibers such as poly(phenylenediamine terephthalamide), graphite fibers, nylon fibers, glass fibers and the like. For many applications, such as vests or parts of vests, the fibers may be used in a woven or knitted fabric. For many of the other applications, the fibers are encapsulated or embedded in a matrix material to form either rigid or flexible fabrics.
Various ballistic resistant constructions are known that are useful for the formation of articles such as helmets, vehicle panels and vests. For example, U.S. Pat. Nos. 4,403,012, 4,457,985, 4,613,535, 4,623,574, 4,650,710, 4,737,402, 4,748,064, 5,552,208, 5,587,230, 6,642,159, 6,841,492, 6,846,758, all of which are incorporated herein by reference, describe ballistic resistant composites which include high strength fibers made from materials such as extended chain ultra-high molecular weight polyethylene. These composites display varying degrees of resistance to penetration by high speed impact from projectiles such as bullets, shells, shrapnel and the like.
For example, U.S. Pat. Nos. 4,623,574 and 4,748,064 disclose simple composite structures comprising high strength fibers embedded in an elastomeric matrix. U.S. Pat. No. 4,650,710 discloses a flexible article of manufacture comprising a plurality of flexible layers comprised of high strength, extended chain polyolefin (ECP) fibers. The fibers of the network are coated with a low modulus elastomeric material. U.S. Pat. Nos. 5,552,208 and 5,587,230 disclose an article and method for making an article comprising at least one network of high strength fibers and a matrix composition that includes a vinyl ester and diallyl phthalate. U.S. Pat. No. 6,642,159 discloses an impact resistant rigid composite having a plurality of fibrous layers which comprise a network of filaments disposed in a matrix, with elastomeric layers there between. The composite is bonded to a hard plate to increase protection against armor piercing projectiles.
It is well known that a small pointed projectile can penetrate armor by laterally displacing fibers without breaking them. Accordingly, ballistic penetration resistance is directly affected by the nature of the fiber network. For example, important factors impacting ballistic resistance properties are the tightness of a fiber weave, periodicity of cross-overs in cross-plied unidirectional composites, yarn and fiber deniers, fiber-to-fiber friction, matrix characteristics and interlaminar bond strengths.
Another important factor affecting ballistic resistance properties is the ability of the ballistic resistant material to resist delamination. In conventional composite ballistic panels, the impact of a projectile on the ballistic fabric layers passes through some of the layers while surrounding fabric layers are stressed or stretched, causing them to fray or become delaminated. This delamination may be limited to a small area, or may spread over a large area, significantly diminishing the ballistic resistance properties of the material, and reducing its ability to withstand the impact of multiple projectiles. Such delamination is also known to occur as a result of cutting sheets of ballistic resistant materials into desired shapes or sizes, causing trimmed edges to fray, and thereby compromising the stability and ballistic resistance properties of the material. Accordingly, there is a need in the art to solve each of these problems.
The present invention provides a solution to these problems. The present invention provides delamination resistant, ballistic resistant materials and articles that are reinforced by various techniques, including stitching one or more ballistic resistant panels with a high strength thread, melting the edges of a ballistic resistant panel to reinforce areas that may have been frayed during standard trimming procedures, wrapping one or more panels with one or more woven or non-woven fibrous wraps, and combinations of these techniques. The invention also provides one or more ballistic resistant panels including one or more rigid plates attached thereto for improving ballistic resistance performance, which may also be reinforced with one or more of the aforementioned techniques. The present invention presents an improvement over U.S. Pat. No. 5,545,455 which does not describe materials reinforced by melting panel edges, nor does U.S. Pat. No. 5,545,455 describe the incorporation of two fibrous wraps which are wrapped in different directions. U.S. patent further does not teach structures that incorporate outer polymer films on their panels, nor structures having rigid plates attached thereto. Articles formed from the materials described herein have been found to have excellent delamination resistance and ballistic resistance properties, which are particularly retained after being stressed by multiple impacts.